the default hasn't been changed since 2009
this can improve our test performances
nixos/tests: remove explicit memorySize <1024
1024MiB is now the default
Following the discussion NixOS#5021:
- obsolete the nix.proxy option
- add the networking.proxy option
- open a default no_proxy environment variable
- add a rsync option
- Manual tests ok.
- Automatic tests ok.
Amended by lethalman to simplify the option descriptions.